<!DOCTYPE html>
<html>
<head>
    <style>
        .error {color : #FF0000}
    </style>
</head>
<body>
<?php
/*
 * 这个是关于表单验证的例子
 * */
$nameError=$emailError=$websiteError=$genderError="";
$name = $email = $gender = $comment = $website = "";
if($_SERVER["REQUEST_METHOD"] == "POST"){
    if(empty($_POST["name"])){
        $nameError = "姓名是必填的！";
    } else {
        $name = test_input($_POST["name"]);
        if(!preg_match("/^[a-zA-Z ]*$/",$name)){
            $nameError = "只允许字母和空格";
        }
    }

    if(empty($_POST["email"])){
        $emailError = "电邮是必须的";
    } else {
        $email = test_input($_POST["email"]);
        if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/",$email)) {
            $emailError = "无效的 email 格式";
        }
    }

    if (empty($_POST["website"])) {
        $website = "";
    } else {
        $website = test_input($_POST["website"]);
        // 检查 URL 地址语法是否有效（正则表达式也允许 URL 中的斜杠）
        if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
            $websiteError = "无效的 URL";
        }
    }

    if (empty($_POST["comment"])) {
        $comment = "";
    } else {
        $comment = test_input($_POST["comment"]);
    }

    if (empty($_POST["gender"])) {
        $genderError = "性别是必选的";
    } else {
        $gender = test_input($_POST["gender"]);
    }
}

function test_input($data){
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}
?>
<h2>PHP 验证实例</h2>
<p><span class="error"> * 必须的字段</span></p>
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
    姓名: <input type="text" name="name" value="<?php echo $name;?>">
    <span class="error">*<?php echo $nameError;?></span>
    <br><br>
    电邮: <input type="text" name="email" value="<?php echo $email;?>">
    <span class="error">*<?php echo $emailError;?></span>
    <br><br>
    网址: <input type="text" name="website" value="<?php echo $website;?>">
    <span class="error"><?php echo $websiteError;?></span>
    <br><br>
    评论: <textarea name="comment" rows="5" cols="40"><?php echo $comment;?></textarea>
    <br><br>
    性别:
    <input type="radio" name="gender" <?php if(isset($gender)&&$gender=="female"){echo "checked";}?> value="female">女性
    <input type="radio" name="gender" <?php if(isset($gender)&&$gender=="male" ){echo "checked";}?>value="male">男性
    <span class="error">*<?php echo $genderError; ?></span>
    <br><br>
    <input type="submit" name="sumit" value="提交">
</form>
<?php
echo "<h2>您的输入: </h2>";
echo $name;
echo "<br>";
echo $email;
echo "<br>";
echo $website;
echo "<br>";
echo $comment;
echo "<br>";
echo $gender;
?>
</body>
</html>